Frequency sweep device having two alternately swept oscillators

ABSTRACT

The frequency sweep operation by two frequency sweep oscillators is reversed whenever the difference in oscillation frequency between the two oscillators reaches a predetermined frequency so that they alternately sweep the frequency step by step. The frequency sweep oscillator device is best suited for use in an automatic channel selector for a television receiver.

United States Patent 1191 1111 3,798,553 Sakamoto 1 Mar. 19, 1974 [5 FREQUENCY SWEEP DEVICE HAVING Jan. 13, 1972 Japan 47/6301 TWO ALTERNATELY SWEPT Jan. 13, 1972 Japan 47/6302 OSCILLATORS [52] U.S. Cl 325/453, 325/421, 325/423, [75] Inventor. Yolchi Sakamoto, Osaka, Japan 55 325/4 3, 328/133, 331/2, 331/4, [73] Assignee: MatsushitaElectric Industrial Co., 331/55, 334/28, 334/86 Osaka, Japan [51] Int. Cl. H04b 1/16 [58] Field of Search 325/418, 421-423, [22] 1972 325/332, 334, 337, 453, 455, 457, 468, 346; [21] Appl. NO.: 224,454 328/133; 331/2, 4, 55; 334/18, 21, 22, 28, 86

[56] References Cited [30] Foreign Application Prlorlty Data Feb. 9, 1971 Japan 46/5738 3 611 152 IL T PATENTS 325/422 a a1 :2: g 12 3322? 2,994,766 8/1961 McCoy 325/334 p 3,665,318 5/1972 Hoffmam. 325/334 Z' 1331 japan 12:;3; 2,661,419 4/1949 Tongue 325/332 e apan.... Feb. 9, 1971 Japan 46/5743 Primary Examiner Albert J Mayer I japan Attorney, Agent, or Firm--Mi1ton J. Wayne e apan Mar. -3. 1971 Japan 46/11430 [57] ABSTRACT Mar. 3, 1971 Japan 46/11431 Mar. 3 1971 Japan 46H 432 The frequency sweep operation by two frequency Mar 1971 la an 46 1900 sweep oscillators is reversed whenever the difference 1971 Japan 416/1190! in oscillation frequency between the two oscillators 1971 Japan H190, reaches a predetermined frequency so that they alter- June 5 1971 Ja an H 46/46146 nately sweep the frequency step by step. The fre- June 5 197] M6141 quency sweep oscillator device is best suited for use in June 1971 3 46/46142 an automatic channel selector for a television re- June 25. 1971 Japan... 46/46143 Jan. 13, 1972 Ja an .1 47/6300 21 Claims, 41 Drawing Figures 1 1, L INTERMEDIATE FREQUENCY AMF'EI IER REFERENCE FREQUENCY GENERATOR 2| 1 l A43. R 51512 ifiia a e n I 10 E6 INDICATOR REFERENCE 2 PULSE FREQ. GEN.

COMPARATOR! 1 PAIENIEDHARIS IIIII 3.798.553

SHE! 01 0F 30 FIG. IA INT RIvI DIAT HIG REQ. IvIIxER FR EQUENCY AMPLIFIER FIRST VOLTAGE 4 LOCALOSC. EPA 55G 5 SECOND SECOND INTERMEDIATE M'XER FREQ. 030.

\ SECOND A66 LOCALOSC. CIRCUIT 9 A VOLTAGE REFERENCE SWEEP FREQUENCY CIRCUIT GENERATOR FIG.|A F|G.IB FIG. IC

FIG.|D

PATENIEDMAR 19, m4 3.798553 sum 02 0F 30 AMPLITUDE DETECTOR s I FREQUENCYi I0 I DETECTOR REFERENCE v FREQ. GEN.

PULSE I SHAPING L T CIRCUIT v r GATE CIRCUIT |3 FL|PFLOP PATENTEDHAR 19 I974 3.798553 sum 03 m 30 E REsET KEY BOARD CIRCUIT 63 V 8 l DECODER V CHANNEL REGISTER NUMBER INDICATOR 2O COMPARATOR ls ,cOuNTER PATENTEI) MR 1 9 I974 SHEET as [If 30 AMPLITUDE DETECTOR 29 3| FREQUENCY REFERENCE DETECTOR FREQUENCY GENERATOR PULSE SHAPING CIRCUIT I GATE A CIRCUIT T '/34 FLIP-FLOP PATENTEDIMR I 9 Ian 3798.553

sum DTUF 30 FIG. 4C

F|G.4A F|G.4B FIG. 4C

39 RESET KEY BOARD CIRCUIT 45 4O\ DECODER CHANNEL REGISTOR 7 NUMBER INDICATOR I 43 REGISTER -42 COUNTER MULTIPLEXERM l l l l 37\ 62 I FLIP-FLOP PATENTEUHAR 1 9 m4 3. 798; 553

saw us or 30 v FREQUENCY MHZ) TIME (Sec) FIG. 7 /5o INTERMEDIATE 52 53 CH FREQUENCY 1/ \l 1 grgllgggg AMPLIFIER L T T T l FIG. 8A Fl. +jx +J'X ll l f f f ////fl I//Izzz 54 I PATENTEDHAR I 9 I974 3798553 SIIIIET #11 IIF,30

68 I I FIRST LOCAL L FIRsT vOLTAOE OSCILLATOR SWEEP CIRCUIT 6S4 65 7 0 HIGH INTERMEOIATE FREQUENCY MIXER FREQUENCY AMPLIFIER AMPLIFIER I SECOND LOCAL REFERENCE FREQUENCY OSCILLATOR GENERATOR SECOND VOLTAGE SWEEP CIRCUIT PATENTED MR 1 9 I974 SHEET '12 0F 30 F|G.lOA

73 8| 7 1 S F RECEIVE A FREQUENCY A EEE5EN8$ CONTROL DETECTOR GENERATOR PANEL 74 V g V 8K2 PULSE I SHAPING REGISTOR CIRCUIT T GATE CIRCUIT 4 COMPARATOR FLIP-FLOP COUNTOR FREQUENCY (MHZ) FIRST REFERENCE FREQUENCY SECOND REFERENCE f,-- FREQUENCY RESET PULSE OUTPUT FROM FREQUENCY DETECTOR PATENIEUMAR 19 I974 JIIEET "15 0F 30 FIG. I?

II-IIIIIII b IDEAL OUTPUT FROM I FREQUENCY DETECTOR IIIIIIIIII OUTPUT FROM C FREQUENCY DETECTOR"| IN PRACTICAL CIRCUIT d RESET PULSE R O A M R O M L W W u U G M N NE K L N PB A, A L UT B 0 e f g BLANKING PULSE B PAIENTED MAR 19 I974 -8HEET 17 or ao A ISZ QZMDOMEL FIG. !9

I IIIIIIIII FREQUENCY DETECTOR OUTPUT FROM llllllllll b FREQUENCY DETECTOR "I" IN PRACTICAL CIRCUIT C RESET PULSE d BLANKING PULSE e OUTPUT OF MONO STABLE MULTIVIBRATOR f BLANKING PULSE 9 INPUTOF FLIP-FLOP WTJULFUTHJTI PATENTEDMAR I 9 I874 3798553 SHEEI 18 0F 30 FIG. 20A

64 7O\ INTERMEDIATE FRE})|8ENCY[: MIXER I AMPLIFIER QfiQt E REFERENCE 5883 3 FREQUENCY-F OSCILLATOR TOR 69 1 II 94 S I SECOND VOLTAGE R- s SWEEP CIRCUIT FLIPFLOP PAIENIEDMAR 19 m4 3,798,553

SHEET T19 0F 30 A FIG. 20A FIGS-".

5 5 A T FREQUENCY REFERENCE RECEIVE FREQUENCY CONTROL DETECTOR GENERATOR PANEL g 8(2 PULSE I SHAPING REGISTOR CIRCUIT v V 83 CI RA LET COMPARATOR v 76 A A 84 FLIP-FLOP COUNTER 

1. A frequency sweep device comprising a first sweep oscillator operating in a first predetermined frequency range, a second sweep oscillator operating in a secoNd predetermined frequency range, first and second alternately operable sweep control means connected to control said first and second sweep oscillators respectively to sweep through the oscillation frequencies in their respective frequency ranges, means for detecting the difference in oscillation frequency between said first and second sweep oscillators, and means for reversing the operable states of said first and second sweep control means whenever the detected difference in oscillation frequency between said first and second sweep oscillators reaches a first or second predetermined frequency, whereby the stepwise frequency sweep can be accomplished alternately by said first and second sweep oscillators.
 2. A frequency sweep device set forth in claim 1 wherein the variation in frequency of one of said first and second sweep oscillators during a period of operation of the corresponding control means is greater than the variation in frequency of the other sweep oscillator during a period of operation of the other control means.
 3. A frequency sweep device set forth in claim 1 comprising starting means for setting one of said first and second sweep oscillators from a predetermined reference frequency.
 4. A frequency sweep device set forth in claim 1 wherein said first and second sweep oscillators each comprise a variable reactance diode, means for applying a reference voltage to one terminal of said variable reactance diode for controlling the frequency sweep, said sweep control means comprise sweep voltage generator means, and the sweep voltage from the respective sweep voltage generator means is applied to the other terminal of said variable reactance diode.
 5. A frequency sweep device set forth in claim 1 which further comprises means for starting alternate operation of said control means, and blanking pulse generating means for blanking the first output occurring of the frequency detection after the sweep has been started.
 6. A frequency sweep device set forth in claim 1 wherein said detecting means for detecting the difference in oscillation frequency between said first and second oscillators includes means for mixing the outputs of said first and second oscillators to produce a first intermediate frequency signal, a third oscillator, mixing means for obtaining a second intermediate frequency signal by frequency-converting said first intermediate frequency signal with the oscillations of said third oscillator, and means for detecting the frequency of said second intermediate frequency signal, whereby said frequency detecting means detects the second intermediate frequency output in order to detect said difference in oscillation frequency between said first and second sweep oscillators.
 7. A frequency sweep device as set forth in claim 1 wherein said detecting means for detecting the difference in oscillation frequency between said first and second sweep oscillators includes first and second reference frequency generators, two phase lock loops and means for alternately applying the output signals from said two reference frequency generators to said phase lock loops in response to the signal representative of said difference in oscillation frequency.
 8. A sweep device set forth in claim 5 comprising means for generating a first pulse having a leading edge coinciding with the first output of said detecting means after the start of alternate operation of said control means, and wherein said blanking pulse generating means comprises means for causing the trailing edge of said blanking pulse to coincide with the trailing edge of said first pulse.
 9. A frequency sweep device as set forth in claim 5 further comprising means generating a first pulse having a leading edge coinciding with operation of said starting means and a trailing edge coinciding with the second output of said detector means after operation of said starting means, and wherein said means for detecting the difference in oscillation frequency between said first and second sweep oscillators comprises two reference frequency generators, and means for temporarily stopping the oscillation of the reference frequency generator corresponding to the frequency to be detected first after the sweep has been started by said first pulse.
 10. A frequency sweep circuit set forth in claim 6 wherein said frequency detecting means for said second intermediate frequency signal comprises a tuned circuit, and piezo-resonators in a portion of said tuned circuit.
 11. A frequency sweep device set forth in claim 6 wherein said detector has an S-shaped characteristic curve, and in order to detect the frequency of said second intermediate frequency signal only at the inner side of the S-shaped characteristic curves, said detecting means comprises means for blanking a detecting pulse which is produced thereby in response to one of said first and second sweep oscillators after starting by said starting means.
 12. A frequency sweep device set forth in claim 6 wherein said means for detecting the frequency of said second intermediate frequency signal includes reference frequency generator means, and phase lock loop means connected to key the signals from said reference frequency generator means in phase and said second intermediate frequency signal.
 13. A frequency sweep device set forth in claim 6 further including reference frequency generator means, means for alternately keying said two sweep control means in phase, a multiplier circuit, means applying the output of said reference frequency generator, and said second intermediate frequency signal to said multiplier circuit in order to detect whether phase locking is accomplished or not, and means for reversing the operation states of said two sweep control means in response to the output from said multiplier circuit.
 14. A channel selecting frequency sweep device comprising a first sweep oscillator operating in a first predetermined frequency range, a second sweep oscillator operating in a second predetermined frequency range, first and second alternately operable sweep control means connected to control said first and second sweep oscillators respectively to sweep through the oscillation frequencies in their respective ranges, means for detecting the difference in oscillation frequency between said first and second sweep oscillators, means for reversing the operable states of said first and second sweep control means whenever the detected difference in oscillation frequency between said first and second sweep oscillators reaches a first or second predetermined frequency, whereby the stepwise frequency sweep can be accomplished alternately by said first and second sweep oscillators, a counter for counting a number of reversals in sweep control operation made between said first and second sweep control means, and means for stopping said reversal and the sweep by said two sweep oscillators when the content of said counter reaches a predetermined value.
 15. A frequency sweep device set forth in claim 14 wherein said means for stopping said reversal and said sweep includes a register for storing a predetermined channel number, a comparator for detecting whether the content in said register coincides with that in said counter or not, and means for stopping said reversal and said sweep when the contents of said register and counter coincides with each other.
 16. A frequency sweep device set forth in claim 14 wherein said means for detecting the difference in oscillation frequency between said two sweep oscillators includes a mixer for mixing the outputs of said two sweep oscillators, an amplifier for amplifying the output from said mixer, and two trap means in said amplifier for detecting said first and second predetermined frequencies.
 17. A channel selecting frequency sweep device comprising a high frequency amplifier, a first sweep oscillator which is a local oscIllator, a mixer for mixing the outputs of said high frequency amplifier and said first sweep oscillator, a second sweep oscillator which is a local oscillator and is connected to the input terminal of said mixer, an intermediate frequency amplifier connected to the output terminal of said mixer, means for detecting whether or not the difference in oscillation frequency between said first and second sweep oscillators which is the output of said intermediate frequency amplifier reaches predetermined first or second frequencies, and means for alternating the frequency sweep operation between said first and second sweep oscillators in response to sequential detection of said first and second frequencies whereby the stepwise frequency sweep can be accomplished.
 18. A frequency sweep device as set forth in claim 17 wherein the difference between said first and second frequencies is 1/n of carrier frequencies of adjacent channels, comprising counter means connected to count said alternate sweep operations of said oscillators, and said counter means counts a number which is 1/n of the number of stopping the sweeps by one of said first and second sweep oscillators, wherein the numeral n designates positive integers.
 19. A frequency sweep device set forth in claim 17 wherein said means for detecting said first and second frequencies include first and second reference generators, and two phase lock loops connected to alternately keying the mixed output signal of the outputs of said first and second sweep oscillators with the output signals from said first and second reference frequency generators respectively, in phase.
 20. A channel selecting frequency sweep device for a signal receiver comprising a high frequency amplifier, a first sweep oscillator which is a local oscillator operating in a first sweep frequency range, a mixer for mixing the outputs from said high frequency amplifier and said first sweep oscillator, a second sweep oscillator which is a local oscillator operating in a second sweep frequency range connected to the input terminal of said mixer, an intermediate frequency amplifier connected to the output terminal of said mixer, first and second alternately operable sweep control means connected to control said first and second sweep oscillators respectively to sweep through the oscillation frequencies in their respective ranges, means for detecting whether the difference in oscillation frequency between said first and second sweep oscillators which is the output of said intermediate frequency amplifier reaches a predetermined first or second frequency or not, means for reversing the operable states of said first and second sweep control means whenever said first or second frequency is detected, whereby the stepwise frequency sweep can be accomplished, a counter connected to count the number of said reversals of one of said two sweep control means, means for stopping the reversing of the operable states of said two sweep control means when the content in said counter reaches a predetermined value, and means for reducing amplification in said high frequency amplifier when said two sweep oscillators are alternately operating.
 21. A frequency detector set forth in claim 20 comprising a main amplifier connected in parallel with said intermediate frequency amplifier. 